The objectives of this program project are (1) to obtain detailed knowledge about how key biological, behavioral, and social developmental processes act together to mediate between early biological risk and subsequent outcome in VLBW infants; (2) to identify specific markers at multiple points in development for detecting the VLBW infant especially at risk for specific problems of development; and (3) to use this knowledge to design and evaluate preventative intervention strategies tailored to identified deleterious processes at specific points in development. The design of the program project and the design and integration of each component study is based on an ecological systems theory perspective and a biopsychosocial transactional model. Premature birth with VLBW is viewed as a stressful condition with associated biological and psychosocial risks that has the potential to become chronically stressful should developmental problems ensue. Developmental outcome is multidimensional, including child developmental outcome and impact on parents and family, and is a function of the interaction of biological and psychosocial risk factor and of mediational factors. Characteristics of the infants, parents, family and environment are the mediational factors. Particular interest is directed to identifying processes associated with movement into or out of at-risk status. Component Project 1 is a longitudinal developmental follow-up study that seeks to establish at multiple points the developmental outcome of VLBW and the impact on parents and to delineate biological and psychosocial risk status. The other component projects were devised to examine in detail two sets of developmental processes thought excellent candidates for either increasing or decreasing biological and/or social risk in VLBW infants. Project 2 examines the biological processes of nutrient utilization and growth during the ICN stay. Project 3 assesses the behavioral processes involve in the impact that unusual infant behavior patterns (e.g. alerting consolability, affective expression) have upon parent-infant interactions.